1. Field of the Invention
The present invention relates to the alignment of a semiconductor device by an aligner, such as a reduction-type projection printing device.
2. Description of the Related Art
Due to the recent trend of ever improving the integration and performance of semiconductor devices, there are demands for finer patterning and higher precision in the lithography technology.
The most typical printing device today is a reduction-type projection printing device (hereinafter called "stepper"). Schemes of aligning a semiconductor device using this stepper include the alignment which uses a laser beam and the alignment which involves image processing.
FIGS. 1 and 3 show the shapes of conventional alignment marks. FIG. 2 is a cross-sectional view taken along the line II--II' in FIG. 1, and FIG. 4 is a cross-sectional view taken along the line IV--IV' in FIG. 3.
Each of the alignment marks comprises recesses 12 and projections 13 formed on an insulating layer 11 on a semiconductor substrate 10. The recesses 12 and projections 13 are alternately arranged on the semiconductor substrate 10. The alignment of the semiconductor device is performed by detecting the edges of the recesses 12 and projections 13 to recognize this alignment mark.